The present invention relates to a device for supplying plastic material for denture base and a flask with the same.
There has been hitherto known a device for supplying plastic material for a denture base, e.g. polymethyl methacrylate (PMMA) as disclosed, for example, in Japanese Unexamined Utility Model Publication No. 145519/1986.
Further, there has been known an art to apply a plastic material, e.g. thermoplastic elastomer, on a backside (to be in contact with a mucous membrane) of a denture in order to form a lining, for example, as disclosed in Japanese Unexamined Patent Publication No. 342/1987.
By blending powder of PMMA with liquified methyl methacrylate (MMA) monomer, kneading the blend to obtain a plastic (dough) material, compressing the material in between a set of plaster models, and heating the material in hot water or vapour of about 100.degree. to 130.degree. C. for a period, the MMA material is polymerized and set, and then a denture base is obtained.
During the initial stage of polymerization, the material expands due to boiling of the liquid MMA monomer, heat-expansion of PMMA, and the like. As polymerization and cooling progress, the material shrinks, and heat-deformation results.
The above-mentioned Japanese Unexamined Utility model Publication No. 145519/1986 disclosed a device having a piston and cylinder for supplying the shortage of PMMA when the material shrinks. However, that device has a drawback in that bubbles and cavities tend to be produced in the denture bases, because the PMMA material expands initially, then shrinks.
Further, the above-mentioned Japanese Unexamined Patent Publication No. 342/1987 discloses a device for forming a liner made of thermoplastic elastomer and for fixing the liner on the backside of a denture base when PMMA material is polymerized and set under heating at the same time. However, the thermoplastic elastomer also expands under heating, and shrinks when cooled. Thus, bubbles and cavities are generated in the resulting liner also.
The main object of the present invention is to provide a device for supplying plastic material for denture base or the like, which does not produce bubbles and cavities in the denture base or the like.